1. Field of the Invention
This invention relates to a magnetic recording medium having a magnetic layer on a non-magnetic base material. More particularly, it relates to a lubricant for the magnetic recording medium whereby improved running properties may be afforded to the magnetic recording medium.
2. Description of the Prior Art
The magnetic recording medium such as the magnetic tape is kept in perpetual contact with guide members or the magnetic heads during running. For this reason, the magnetic recording medium is required to have a low frictional coefficient and highly stable running characteristics. It is also required to be superior in wear resistance because it is in vigorous frictional contact with the guide members or magnetic heads with a high relative speed during recording and reproduction.
For improving the running properties or wear resistance of the magnetic recording medium, there has so far been known a method which consists in adding a lubricant to the magnetic layer, or forming a lubricant layer on the surface of the magnetic layer. The lubricant may generally include a solid lubricant such as molybdenum disulfide, graphite or wax, higher fatty acids, esters thereof with monohydric alcohols, or silicone oil.
With use of these lubricants, good running properties can be afforded to the magnetic recording medium. However, in this case, the other properties of the magnetic tape tend to be lowered. For example, the solid lubricant is not effective in improving the durability of the magnetic recording medium and, if used in excess amounts, may undesirably deteriorate its magnetic properties. On the other hand, the fatty acids etc. used as the lubricant are not only unable to impart sufficient lubricity to the magnetic recording medium but also may deteriorate its running properties through ageing. In addition, when added into the magnetic layer, the lubricant material may give rise to blooming which in turn may cause adherence or stick slip of the magnetic recording medium.